This invention relates to heating apparatus and, more particularly, to a semiautomatically controlled forced draft and forced fluid heat exchange system for a solid fuel burner. The invention is particularly well suited for use with a residential fireplace and will be described principally with reference thereto; however, it is capable of broader application and could be used on many types of solid fuel burners such as wood and coal stoves.
Fireplaces and stoves have been used to provide residential heat for many years. Although once the predominant form of heating and cooking, these devices declined in importance as central home heating systems and gas and electric stoves became the norm. During this period, until only recently, the traditional fireplace and stove were built more for appearance than function. They were no longer necessities, only aesthetic fixtures intended for occasional use. Consequently, there was little incentive to improve upon the inefficiencies of the traditional installations.
In recent years, however, the rising cost of fossil fuels and the energy consciousness of this country have renewed interest in the fireplace and stove as sources of heat. Many home owners, hoping to reduce their consumption of increasingly expensive fossil fuels, attempt to rely upon their existing fireplaces and stoves as supplemental sources of heat only to find them grossly inefficient. This invention permits a homeowner to substantially increase the efficiency of his existing fireplace or stove, thereby rendering it of practical value without destroying its aesthetic value. In addition, the invention may be incorporated into new installations with comparable results.
One of the most important factors affecting fireplace efficiency is the method of discharging the combustion products. In order to function efficiently, a fireplace requires a substantial draft. In typical fireplaces, sufficient draft is achieved by providing a flue having a large cross sectional area. To prevent the loss of heated room air when the fireplace is not in use, a manual damper is used. A problem with this system is that unless the damper is manually closed after the fire dies out, heated room air is drawn up the flue. Another disadvantage of the traditional system is that even with proper draft, most of the heat generated by the fireplace goes up the flue with the exhaust gases.
There have been many attempts to improve upon these inefficiencies. Heat exchangers of various types have been mounted in the fireplace and blowers have been placed in the flue to improve draft conditions. Each of these efforts has been unsatisfactory for one or more reasons: they are complex, expensive, inconvenient to operate, difficult to install, or incomplete in meeting the problems. For example, the forced draft blower disclosed in U.S. Pat. No. 3,782,303 to Pfister, although of some benefit in terms of creating a substantial draft through a burner, suffers from the disadvantages of manual control. As a result, the inefficiencies caused by improperly modulated draft, such as excessive heated room air loss, persist.